Auxiliary electrode



July 23, 1935. RANDALL r AL 2,009,205

AUXILIARY ELECTRODE Filed March 14, 1935 ATTORN EY Patented July 23,1935 UNITED STATES PATENT OFFICE AUXILIARY ELECTRODE poration of NewYork Application March 14, 1935 Serial No. 11,152 In Great Britain March14, 1934 5 Claims'.' '(Cl. 176126) This invention relates to auxiliaryelectrodes for facilitating the starting of an electric dischargebetween the main electrodes of an electric discharge device, and moreparticularly the in- 5 vention relates to auxiliary electrodes of thetype placed in the neighbourhood of a main electrode and connectedelectrically either to the other main electrode or to an auxiliaryelectrode in the neighborhood of that other main elec- 10 trade.

Auxiliary electrodes of the type having a multiplicity of dischargesupporting points directed towards the associated main electrode arelong lived as the life thereof is not limited by the 15 wearing away ofa single point. The object of this invention is to provide a simple andefficient electrode of this kind. Another object of the invention is toprovide a method of manufacture of the electrodes of this type. Stillfurther objects and advantages attaching to the device and to its useand operation will be apparent to those skilled in the art from thefollowing particular description.

According to the invention an auxiliary elec- 25 trode for facilitatingthe starting of an electric discharge is made by winding a metal wire orfilament in the form of a helix about a plurality of substantiallyparallel support wires, which wires are supported by a mandrel havinggrooves 30 therein to accommodate said support wires, fixing the turnsof the helix to a support wire where they are in contact with it,preferably by welding, and then cutting the helix substantially in aplane parallel to the said support wires.

3.": Preferably the plane is equidistant from the support wires andperpendicular to the plane containing them. The result is then a pair ofcombs, each of which has two rows of teeth consisting of the portions ofthe helix fixed to one support 40 wire, the two rows being inclined toeach other at an angle that is preferably acute.

The support wire is of nickel, when desired;

the helix, parts of which constitute the teeth of the double comb, ispreferably of a more refrac- 45 tory metal, such as molybdenum ortungsten; the diameter of the wire of the helix is, preferably, about0.07 mm. When desired, the support wire is also of molybdenum ortungsten. The teeth should be closely spaced, for instance 30 per 50 cm.The two rows of teeth are freed from gas, for example by treatment in avacuum furnace, before being mounted in the discharge device; this isusually necessary in order to secure regular operation of the dischargedevice.

55 The auxiliary electrode thus formed has teeth a few millimeters longand is placed a few millimeters from the main electrode with its teethturned towards that electrode. Preferably it is placed so that the planebisecting the angle between the two rows of teeth passes through themain electrode. If the main electrode is a rod, the said plane ispreferably parallel to the length of the rod.

In the drawing accompanying and forming part of this specification anembodiment of the invention is shown in which Fig. 1 is a frontelevational, partly sectional view of a gaseous electric discharge lampdevice having an auxiliary electrode embodying the invention,

Fig. 2 is a sectional view along the line 22 of Fig. 1,

Fig. 3 is a side elevational view of one step in the manufacture of anelectrode embodying the invention, and

Fig. 4 is a sectional view along the line 4-4 of Fig. 3.

Like numbers denote like parts in all the fig- UIGS.

Referring to Figs. 1 and 2 of the drawing the gaseous electric dischargelamp device comprises an elongated, tubular, glass container l having amain discharge supporting electrode 2, 3 sealed into each end thereof.Said electrodes 2, 3 each comprise a rod or bar 2 of electron emittingmaterial, such as an alkaline earth compound, and a metal heaterfilament 3, such as a tungsten filament. The longitudinal axis of eachof said rods 2 is parallel with the longitudinal axis of said containerl. The ends of said filament 3 are sealed into the press part of thestems of said container 1 and are connected to the current leads 4 and5. An auxiliary electrode '1, 8 made in accordance with the presentinvention is also sealed into said container I. Said electrode 1, 8 con-40 sists of a support wire I, such as a nickel wire, and a multiplicityof pointed wires 8 welded to said support wire I. Said wires 8 arearranged in two rows extending in parallel directions, said rows beingat an acute angle, such as an angle of approximately 30 degrees, to eachother. The support wire l is parallel to the axis of the rod 2 of saidelectrode 2, 3, and is sealed into the press part of the stem of thecontainer I. Current lead I0 is connected to said support wire 1 andsaid lead i0 is also connected through a high resistance to a terminalof the current source for said device other than that terminal to whichthe main electrode 2, 3, to which said auxiliary electrode I, 8 isadjacent, is connected. Said container 1 has a gaseous atmospheretherein, such as a rare gas, a mixture of gases, a metal vapor, amixture of metal vapors, or a mixture of gas and metal vapor. During thestarting period a multiplicity of auxiliary discharges takes placebetween the points of said wires 8 and spots on said electrode 1, 8which rapidly heat these members to cause a proliflc emission ofelectrons to facilitate the starting of the main discharge between themain electrodes I, 8.

In the manufacture of the auxiliary electrodes 1, 8 two support wires 1,such as nickel wires, are placed in grooves in opposite edges of amandrel 9 which is a rhomboid in cross-section (Figs. 3 and 4). Thesides of the mandrel 9 on either side of the grooves in said mandrel areat an angle of approximately 30 degrees to each other. A metal wire 8,such as a molybdenum wire, is then wound around said mandrel 9, theturnings of said wire 8 being approximately 30 per cm. along saidwires 1. The support wires I and the wire 8 are then welded together atthe points of contact therebetween. Wire 8 is then cut, as

' by grinding, along the corners of the mandrel 9 having no groovestherein. Two electrodes each having a support wire 1 and two rows ofpointed wires 8 are thus manufactured. The two rows of pointed wires 8are at an acute angle of approximately 30 degrees to each other. It willbe understood, of course, that I contemplate that the steps in the abovemethod can be varied when desired, for example, the wire 8 is firstwrapped around the mandrel and the support wires 1 are then brought intocontact with the wire 8 outside the turnings of said wire 8; the stepsof welding and cutting are then performed as above.

The auxiliary electrode is preferably mounted in the discharge device insuchmanner that a plane bisecting the angle between the two rows ofwires 8 has the longitudinal axis of the rod 2 therein and the points ofwires 8 are approximately 4 mm. from the surface of the rod 2.

What we claim as new and desire to secure by Letters Patent of theUnited States, is:-

1. An electrode for an electric discharge device, said electrodecomprising a support wire having a multiplicity of other wiresprojecting therefrom substantially at right angles thereto, said lastnamed wires being in two parallel rows along said support wire, saidrows being at an acute angle to each other.

2. The method of manufacturing electrodes for electric discharge deviceswhich consists in the steps of mounting a pair of support wires inopposite parallel positions on a mandrel, wrapping another wire aroundsaid mandrel, said support wires and said wound wire being in contact atnu merous points along the length thereof, welding said wires togetherat the points of contact therebetween and cutting said wound wire onsaid mandrel in a plane perpendicular to the plane of said support wiresintermediate said support wires.

3. The method of manufacturing electrodes for electric discharge deviceswhich consists in the steps of winding a wire around a mandrel, bringinga pair of support wires into contact with said wound wire, saidsupportwires being in opposite parallel positions, welding said supportwires and said wound wire together at the points of contact therebetweenand cutting said wound wire in a plane perpendicular to the plane ofsaid support wires and intermediate said support wires. 4. The method ofmanufacturing electrodes for electric discharge devices which consistsin the steps coiling a wire, bringing a pair of parallel support Wiresinto contact with said coiled wire, welding said support wires to saidcoiled wire and cutting said coiled wire in a plane perpendicular to theplane of said support wires and intermediate said support wires.

5. An electric discharge device comprising a container, electrodessealed therein, a gaseous atmosphere sealed therein, one of saidelectrodes being a main discharge supporting, elongated, thermionicelectrode, another of said electrodes being an auxiliary electrodemounted adjacent said main electrode, said auxiliary electrodecomprising a support wire having a multiplicity of other Wiresprojecting therefrom substantially at right angles thereto, said lastnamed wires being in two parallel rows along said support wire, saidrows being at an acuate angle to each other, said support wire beingsubstantially parallel to said elongated, main electrode, thelongitudinal aXis of said main electrode being in a plane bisecting theangle between the parallel rows of wires of said auxiliary electrode.

JOHN 'I'URTON RANDALL. NORMAN LESLIE HARRIS. JOHN WALTER RYDE.

